A 20 mK temperature sensor

The authors report tests of a 20-mK temperature sensor made of neutron-transmutation-doped (NTD) germanium, which they have developed for use as a phonon detector in a dark matter search. Current-voltage, responsivity, and AC measurements have been made, and the minimum detectable energy has been estimated. They have found that NTD germanium thermistors around 20 mK have resistances that are a strong function of temperature and have sufficient sensitivity to eventually reach a base line RMS energy fluctuation of 6 eV at 25 mK. The authors consider that further work is needed to understand the extreme sensitivity of the thermistors to bias power.<
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